[postgis-devel] Re: [HACKERS] join selectivity

[strk at refractions.net]

On Thu, Dec 23, 2004 at 10:01:33AM -0500, Tom Lane wrote:
> strk at refractions.net writes:
> > Doing some tests I've found out that the returned value from the
> > JOINSEL is applied to REL1.rows X REL2.rows, but REL1 and REL2
> > are not 'base' table, rather relations with a number of 
> > rows once again estimated by other selectivity functions.
> 
> Right.  This amounts to assuming that the join conditions and the
> restriction conditions are independent, which of course is bogus,
> but we really don't have enough information to do better.
> 
> 			regards, tom lane

Doesn't JOINSEL have access to RESTRICTSEL output for REL1 and REL2 ?

--strk;